1. Field of the Invention
The invention is related to guidewires used for the insertion of catheters into the vascular system or other internal body cavities such as the urethra, brain, biliary etc. as a method of treating disease or delivering a catheter or stenting device to open or hold open a segment of the vessel or pathway.
2. Description of the Prior Art
As a treatment technique for removing blockages in the vascular system, particularly those which affect the blood supply to the heart or brain, guidewires of very fine diameter are inserted directly into the system from outside the patient and manipulated or steered by the physician or practitioner through the system to the blockage by fluoroscopic observation. Since the various vessels through which the wire must pass are sinuous or irregular in shape and intersect and connect with other vessels at various and sometimes sharp angles, maneuvering the wire to the position of concern is a delicate task. The catheters designed for dilating or stenting these areas are generally not steerable devices and need to be advanced over a guide wire to locate the area desired.
Guide wires which are steerable are unlike standard guide wires which merely assist entering the body by providing a rail over which a catheter may be advanced for safely entering the pathway without scraping the surface they are entering. Steerable wires have the ability to be directed or torqued in order to direct the tip which has either a preformed tip or one formed by the user to match the requirements of the pathway. Once torqued in the desired direction they are advanced in the appropriate direction.
A plurality of guidewire type devices designed for this purpose exist in the prior art. Each is a novel approach to the problem of providing the user with sufficient control to transverse a pathway in a speedy and careful manner. For example, U.S. Pat. Nos. 4,545,390, Leary, and 3,789,841, Antoshkiw, both show distal tips formed of helically wound springs surrounding fixed tapered cores. U.S. Pat. No. 3,631,848, Muller, describes an axially movable distal tip extension tube of relatively short length.
A coil tip with tapered face edges which will curve toward the taper when pulled upon by an internal control wire is disclosed in U.S. Pat. Nos. 3,452,740, and 3,452,742, both to Muller. U.S. Pat. No. 4,650,467, Bonello shows a similar arrangement for inclining the tip by retraction of a control wire affixed thereto.
Additionally, U.S. Pat. No. 3,528,406, Jeckel et al. teaches the use of a fixed core wire having a reduced diameter in the spring tip portion of the wire. U.S. Pat. No. 3,625,200, Muller, discloses a curvable tip comprising solid cylindrical links engaging each other with ball and socket joints each of which is manipulatable by a fine core wire. U.S. Pat. No. 4,573,470, Samson shows a curved tip which is rotated in its entirety by rotating a core wire at the control handle.
Finally, U.S. Pat No. 4,783,983 teaches the use of a moveable core to straighten and stiffen the end of a steerable guide wire by advancing the core to the tip of the guide wire thus overcoming the bend of the safety wire.
The present invention is an improved guidewire which allows the user to vary the stiffness and support of the wire and vary the curvature of the tip from outside the patient during the transport and manipulation process by either retracting the core thus straightening a pre-formed tip segment, or in the case of the spring segment with restraining wire, advancing/pushing the core wire to force the distal segment to bend in one plane forming a curve the length of which is determined by the length of the spring being restrained and/or exposed past the end of the catheter or tube from which it extends.
The invention may be summarized as a guidewire of the type of and for the above described purpose consisting of a distal portion comprising two helically wound springs of differing material and the distal spring having a smooth rounded tip attached to the core, and a proximal portion comprising a length of tubing joined at the proximal end of the spring to form a continuous unit. A core wire tapered at the distal end is moveably disposed within the tubing and spring such that the amount of flexibility or floppiness of the spring may be varied by moving the core wire to various positions along the length, thus tensioning the distal spring segments. The distal core is swaged to allow for added flexibility while maintaining torque and for forming the distal tip segment to the desired curve and for eliminating the need for a separate safety wire to contain the coils whilst retaining flexibility and torque. When the core is advanced the distal tip may assume a curve as a result of the bias of the swaged core. With the core wire fully retracted the spring tip is straightened facilitating the penetration (crossing) of the lesion or partial blockage. A handle attached to the proximal tube segments allows for retracting or advancing the core and for imparting torque simultaneously to the guide wire tube or independently to the core thus torqueing either the entire guide wire or merely the distal spring segment thus avoiding the resistance to torque of the catheter through which the guide wire may be placed. To further facilitate crossing narrowings, the spring segment may be tapered forward of the tube segment.
Alternatively an additional smaller wire may be disposed within the tip end of the spring which prevents the spring coils from separating and allows a shape to be imparted to the tip when the core is advanced distally to tension the tip. The small wire is sufficiently thin to allow the tapered core wire to move freely within the spring segment. Thus with the core wire partially withdrawn, the end of the spring will straighten and stiffen as the core is attached to the distal spring coil. When the core is advanced the distal tip may assume a curve as a result of the tension on the swaged core forcing it to bend while being restrained by the smaller wire and surrounding spring segments. The design allows for a low profile device with sufficient strength to bend a catheter through which it is placed and to provide torque to the catheter for directing the catheter which has been bent in the desired direction.
These and other features and objects of the invention will become clearer from the following drawings and description of the preferred embodiment.